Image-capturing device

1. An image-capturing device, comprising: an input unit that inputs a subject image formed by an optical system manifesting axial chromatic aberration as an input image; an edge detection unit that detects edges in the input image input by the input unit, each in correspondence to one of color components; a focus adjustment unit that executes focus adjustment for the optical system by detecting contrast differences of the edges corresponding to individual color components having been detected by the edge detection unit and then moving a focus adjustment lens included in the optical system; a lens moving direction determining unit that determines a moving direction along which the focus adjustment lens is to move for purposes of focus adjustment based upon a difference between the edges corresponding to the individual color components having been detected by the edge detection unit and the axial chromatic aberration; a resolution change correction unit that corrects a resolution change occurring in relative resolution levels of the individual color components due to a factor other than the axial chromatic, aberration, based upon the edges corresponding to the individual color components having been detected by the edge detection unit; and a calculation unit that calculates a blurring width difference indicating a difference between edge blurring widths of edges corresponding to two color components each manifesting the axial chromatic aberration among, the edges of the individual color components having been detected by the edge detection unit, wherein: the lens moving direction determining unit determines the moving direction along which the focus adjustment lens is to move based upon the blurring width difference having been calculated by the calculation unit, the blurring width difference is calculated by the calculation unit based upon the edges corresponding to the individual color components detected by the edge detection unit from an image having been corrected by the resolution change correction unit for any resolution change in relative resolution levels of the individual color components, and the focus adjustment unit causes the focus adjustment lens to move along the moving direction determined by the lens moving direction determining unit.

2. An image-capturing device according to claim 1 , wherein: the calculation unit calculates a specific evaluation value based upon a color difference sum of color differences for the edges corresponding to the two color components manifesting the axial chromatic aberration and calculates the blurring width difference by using the evaluation value thus calculated.

3. An image-capturing device according to claim 2 , wherein: the calculation unit divides the edges corresponding to the two color components manifesting the axial chromatic aberration into a flat portion and an edge portion and calculates the color difference sum for the edge portion.

4. An image-capturing device according to claim 1 , wherein: the calculation unit individually measures the edge blurring widths of the edges corresponding to the two color components manifesting the axial chromatic aberration and calculates the blurring width difference based upon measurement results.

5. An image-capturing device according to claim 1 , wherein: the calculation unit calculates the blurring width difference based upon the edge blurring widths and edge gradients of the edges corresponding to the two color components manifesting the axial chromatic aberration, as well as the contrast differences each manifesting between two sides of one of the edges.

6. An image-capturing device according to claim 1 , wherein: the calculation unit calculates the blurring width difference based upon edge brightness areas of one of the edges corresponding to the two color components manifesting the axial chromatic aberration and the contrast differences each manifesting between two sides of an edge.

7. An image-capturing device according to claim 1 , further comprising: a color correction unit that executes correction so as to eliminate the contrast differences each manifesting between two sides of one of the edges corresponding to the two color components manifesting the axial chromatic aberration, wherein: the calculation unit calculates the blurring width difference by using an image resulting from the correction executed by the color correction unit.

8. An image-capturing device according to claim 1 , wherein: the calculation unit calculates the blurring width difference only after executing up-sampling processing on the input image.

9. An image-capturing device, comprising: an input unit that inputs a subject image formed by an optical system manifesting axial chromatic aberration as an input image; an edge detection unit that detects edges in the input image input by the input unit, each in correspondence to one of color components; a focus adjustment unit that executes focus adjustment for the optical system by detecting contrast differences of the edges corresponding to individual color components having been detected by the edge detection unit and then moving a focus adjustment lens included in the optical system; and a lens moving direction determining unit that determines a moving direction along which the focus adjustment lens is to move for purposes of focus adjustment based upon the edges corresponding to the individual color components having been detected by the edge detection unit and the axial chromatic aberration; and a selection unit that selects two color components manifesting the axial chromatic aberration among color components constituting the input image; and a calculation unit that calculates a blurring width difference indicating a difference between edge blurring widths of edges corresponding to two color components selected by the selection unit, wherein: the selection unit selects pixels representing two color components, to be used to achieve uniformity of resolution, which assumes varying levels due to a factor other than axial chromatic aberration, in correspondence to a direction of an edge present in the input image; the lens moving direction determining unit determines the moving direction along which the focus adjustment lens is to move based upon the blurring width difference having been calculated by the calculation unit; and the focus adjustment unit causes the focus adjustment lens to move along the moving direction determined by the lens moving direction determining unit.

10. An image-capturing device according to claim 9 , wherein: the input image is a raw image generated through a pixel sum read.

11. An image-capturing device according to claim 10 , wherein: the selection unit selects the pixels representing the two color components, to be used to achieve uniformity of resolution, which assumes varying levels due to a factor other than the axial chromatic aberration, by taking into consideration a positional relationship between pixel positions assumed by pixels representing various color components in an initial raw image read out from an image sensor and pixel positions assumed by pixels representing the various color components in the raw image generated through the pixel sum read.

12. An image-capturing device according to claim 9 , wherein: the input image is an image having undergone interpolation processing.

13. An image-capturing device according to claim 1 , wherein: occurrence of the resolution change in relative resolution levels of the individual color components is attributable to a pixel sum read from an image sensor or image processing.

14. An image-capturing device according to claim 1 , wherein: the resolution change in relative resolution levels of the individual color components has dependency on an edge direction relative to a pixel array assumed for pixels constituting the image, colors assumed on two sides of the edge, the shape of the edge and a condition in the optical system.

15. An image-capturing device according to claim 1 , wherein: the resolution change correction unit corrects the resolution change by applying a smoothing filter assuming a preselected coefficient to pixels representing a color component, a resolution level of which is to match the resolution level of another color component.

16. An image-capturing device according to claim 1 , wherein: the resolution change correction unit corrects the resolution change by applying an edge enhancement filter assuming a preselected coefficient to pixels representing a color component, a resolution level of which is to match the resolution level of another color component.

17. An image-capturing device according to claim 15 , wherein: the resolution change correction unit alters the coefficient based upon edge characteristics unique to the input image.

18. An image-capturing device according to claim 1 , further comprising: an edge area image extraction unit that extracts from the input image an edge area image containing the edges corresponding to individual color components having been detected by the edge detection unit, wherein: the lens moving direction determining unit determines the moving direction along which the focus adjustment lens is to move by using the edge area image having been extracted by the edge area image extraction unit.

19. An image-capturing device according to claim 18 , further comprising: a color correction unit that executes color correction so as to eliminate a color difference manifested between two sides of an edge in the edge area image having been extracted by the edge area image extraction unit, wherein: the lens moving direction determining unit determines the moving direction along which the focus adjustment lens is to move by using the edge area image having undergone the color correction executed by the color correction unit.

20. An image-capturing device according to claim 19 , wherein: the color correction unit executes the color correction by normalizing color ratios of the individual color components in areas on the two sides of the edge so that the color ratios achieve a specific value.

21. An image-capturing device according to claim 19 , further comprising: a magnification chromatic aberration correction unit that executes magnification chromatic aberration correction to correct any chromatic aberration of magnification manifesting in the edge area image having undergone the color correction executed by the color correction unit, wherein: the lens moving direction determining unit determines the moving direction along which the focus adjustment lens is to move by using the edge area image having undergone the magnification chromatic aberration correction executed by the magnification chromatic aberration correction unit.

22. An image-capturing device according to claim 21 , wherein: the magnification chromatic aberration correction unit executes the magnification chromatic aberration correction by shifting charts each indicating edge intensity corresponding to one of the color components within the edge area image so as to reduce an extent of offset manifested by the charts corresponding to the individual color components.

23. An image-capturing device according to claim 18 , further comprising: a usability determining unit that determines whether or not the edge area image having been extracted by the edge area image extraction unit can be used to determine the moving direction along which the focus adjustment lens is to move, wherein: the lens moving direction determining unit determines the moving direction along which the focus adjustment lens is to move by using the edge area image determined to be usable by the usability determining unit.

24. An image-capturing device, comprising: an input unit that inputs a subject image formed by an optical system manifesting axial chromatic aberration as an input image; an edge detection unit that detects edges in the input image input by the moving direction, each in correspondence to one of color components; a focus adjustment unit that executes focus adjustment for the optical system by detecting contrast differences of the edges corresponding to individual color components having been detected by the edge detection unit and then moving a focus adjustment lens included in the optical system; and a lens moving direction determining unit that determines a moving direction along which the focus adjustment lens is to move for purposes of focus adjustment based upon the edges corresponding to the individual color components having been detected by the edge detection unit and the axial chromatic aberration; an edge area image extraction unit that extracts from the input image an edge area image containing the edges corresponding to individual color components having been detected by the edge detection unit; and a usability determining unit that determines whether or not the edge area image having been extracted by the edge area image extraction unit can be used to determine the moving direction along which the focus adjustment lens is to move, wherein: the usability determining unit determines the edge area image to be usable if an extent of offset manifested by charts each indicating edge intensity corresponding to one of the color components within the edge area image, is less than a predetermined offset quantity; the lens moving direction determining unit determines the direction along which the focus adjustment lens is to move by using the edge area image determined to be usable by the usability determining unit; and the focus adjustment unit causes the focus adjustment lens to move along the moving direction determined by the lens moving direction determining unit.

25. An image-capturing device according to claim 18 , wherein: the lens moving direction determining unit determines the moving direction along which the focus adjustment lens is to move by calculating an index value for the edge area image, to be used when determining the direction along which the focus adjustment lens is to move, and comparing the index value with a preselected threshold value.

26. An image-capturing device according to claim 25 , wherein: the lens moving direction determining unit calculates the index value based upon a color ratio pertaining to a color component manifesting an axial chromatic aberration different from axial chromatic aberration of another color component, among the individual color components in the edge area image.

27. An image-capturing device according to claim 25 , further comprising: a history recording unit that records index value history indicating values previously calculated for the index value, wherein: the lens moving direction determining unit sets the threshold value based upon the index value history recorded by the history recording unit.